1. Field of the Invention
The invention relates to a liner hanger apparatus for use in carrying and setting a casing liner within an enlarged diameter casing section within a subterranean well.
2. Description of the Prior Art
Subsequent to the drilling of a subterranean oil or gas well, metallic casing is run into the well and cemented into place therein. The casing string normally comprises telescoping sections, the sections being of considerable length relative to the depth of the well. As the well depth increases, the internal diameter of the casing sections will become smaller such that they are positioned in the well in somewhat telescopic mode. Each of the casing sections below the first or main casing is called a "liner" and is run into the well within the casing on a tubular workstring with the liner being set immediate the lowermost end of the casing by means of a "liner hanger". Typically, such liner hangers are either mechanically actuated and/or hydraulically actuated and comprise a slip mechanism to grasp the interior wall of the casing such that the hanger is in gripping engagement with the casing and the liner extends below the hanger and is secured to the lowermost end thereto.
Recent technological advances have contributed to the successful concept of horizontal drilling and completion operations. In past vertical well operations, it has been necessary for the liner hanger to only hold longitudinal movement of the liner and/or workstring (while it is secured to the hanger) against movement in one direction, i.e. downward movement, attributable to the weight carried through the hanger by the length of the extending liner therebelow. However, in the case of horizontal wells, as well as in some other well applications, it becomes necessary for the liner hanger to hold in both directions.
In the past, those skilled in the art have provided liner hangers having two sets of slip assemblies, one slip assembly holding the hanger and resisting movement in one direction while the other slip assembly has held the liner hanger and prevented movement in the other direction. The provision of plural sets of slips not only is costly, but contributes to the weight and complexity of the apparatus and the various setting mechanisms utilized to set such slips. In such instances, while such slip assemblies have been designed to be satisfactory, such design must take careful consideration of the setting mechanism and procedure to assure that both sets of slip elements are properly and completely set to assure that there is no imbalance between the respective sets with respect to the holding.or gripping action relative to the casing.
Regardless of the slip assembly configuration in liner hangers, when the hangers are hydraulically actuated, the slip assembly will only receive approximately 5 to 6 thousand p.s.i. of force, which is the maximum force which can be transmitted through the tool by means of application of hydraulic pressure through the workstring and the interior of the liner hanger. In contrast, hangers which are actuated into set condition by means of mechanical manipulation of the tubular workstring, either longitudinally and/or rotationally, can receive from between 50 to 100 thousand pounds of load through the slip assembly.
In the past, those skilled in the art have been unable to manipulate a tubular workstring into rotational movement while also preventing movement in both directions. In some instances in completion operations, it would be desirable to permit the workstring to rotate through the liner hanger to transmit torque through the liner conduit to activate valves, float shoes, or the like during cementing and other completion and remedial operations.
The present invention is directed to providing a liner hanger apparatus which remedies the problems in prior art
devices, as above described.
In U.S. Pat. No. 4,750,563, entitled "Slip Gripping Mechanism With Automatic Segment Alignment", and assigned to Hughes Tool Company, a predecessor entity to Applicant's assignee, there is shown and disclosed a slip gripping mechanism which can be utilized in a hanger assembly. Additionally, in U.S. Pat. No. 4,711,326, entitled "Slip Gripping Mechanism", also assigned to Hughes Tool Company, a predecessor entity of the assignee of the present invention, there is shown and disclosed a slip assembly which is similar to that of the present invention and which can be adapted for use in liner hangers. However, neither of these slip assemblies will hold the assembly in set condition against movement in both directions as a result of force being applied across the tool from bottom to top or top to bottom. Additionally, neither of these devices is initially moved to set condition by means of hydraulic actuation with subsequent mechanical load being applied to the set slip assembly. Furthermore, neither of these prior art devices contemplate incorporation into a hanger which may be rotated to rotate the liner section carried therebelow without rotational effect upon the set slip assembly which is in gripping engagement with the interior wall of the casing conduit.